1. Field of the Invention
The present invention relates to a technique for an image quality adjustment, and more particularly, to a technique for a color adjustment made by a user with a graphical interface.
2. Description of the Related Art
In an image quality adjustment of a television, a digital camera, etc., the demand for a color adjustment that a user can more freely make, such as the demand that a user freely adjusts the skin color of a person, green colors of plants and trees, etc. based on his or her preferences has been increasing.
For manual image quality adjustment techniques, a variety of techniques such as retouch software, etc. conventionally exist. As these color adjustment methods, a method with which a user specifies and one-dimensionally adjusts an arbitrary color respectively for lightness, chroma and hue, or a method with which a user specifies an arbitrary color in a two-dimensional display of chroma and hue are provided (for example, Patent Documents 1, 2 and 3). With these methods, changes in a target color to be adjusted before and after a correction can be presented to a user.
An example of a user interface for making a one-dimensional color adjustment is shown in FIG. 1A. If a yellowish hue is changed to a greenish hue via the user interface shown in FIG. 1A, a desired color adjustment can be made by specifically inputting the value of a hue to a text box to set the value.
FIG. 1B exemplifies a user interface for making a two-dimensional color adjustment. Via the user interface shown in FIG. 1B, a point indicated by an arrow in this figure is specified, for example, with a pointing device to simultaneously specify chroma and hue, and specific values are input to text boxes in the right portion of this figure, whereby a desired color adjustment can be made simultaneously for chroma and hue.
FIG. 2 is a schematic (No. 1) explaining a color adjustment method for 3 attributes according to a conventional technique. Adjustment ranges of lightness, chroma and hue are respectively specified for a region, which includes a target color to be adjusted, in the neighborhood of the target color, and a color adjustment is made to an arbitrary region including the target color to be adjusted.
FIG. 3 is a schematic (No. 2) explaining a color adjustment method for 3 attributes according to a conventional technique. With a color adjusting apparatus shown in FIG. 3, a target color to be adjusted is specified, and a lightness adjustment value, a chroma adjustment value, and a hue adjustment value are specified respectively for the values of the attributes, whereby a color adjustment can be made more flexibly.
[Patent Document 1] Japanese Published Unexamined Patent Application No. H8-321957
[Patent Document 2] Japanese Published Unexamined Patent Application No. 2003-125221
[Patent Document 3] Japanese Published Unexamined Patent Application No. 2003-250058
For example, with the technique disclosed by Patent Document 1, a color adjustment is made by adopting a matrix operation of a masking process. Therefore, the ranges of lightness and chroma cannot be specified when a color is selected. Namely, only a control for the range of hue can be implemented in the masking process.
Additionally, with the technique disclosed by Patent Document 2, the adjustment amounts of neighboring colors including a target color are made equal, and a control for gradually changing and reducing the adjustment amounts in order to smoothly maintain tones cannot be performed in the neighborhood of the boundary of an adjustment range. This leads to a problem that the degree of freedom of a control for the color adjustment is insufficient.
Furthermore, the technique disclosed by patent Document 3 has a problem that a control for setting adjustment values respectively for the adjustment values of the lightness, chroma and hue of a target color specified by a user becomes complex. Namely, adjustment values respectively for the lightness, chroma and hue must be set for the lightness of the target color, adjustment values respectively for the lightness, chroma and hue must be set for the chroma of the target color, and adjustment values respectively for the lightness, chroma and hue must be set for the hue of the target color. In this way, a user must perform operations for an adjustment by grasping 3×3=9 items, leading to the complexity of the control for the color adjustment. Accordingly, there is a problem that difficulties exist in the intuitive grasping of the state of the target color and the contents of the adjustment.
Furthermore, the color adjustment methods according to the conventional techniques do not comprise means with which a user grasps the states, which include states before and after an adjustment, of other colors positioned in the neighborhood of a target color to be adjusted, although the states of the target color before and after the adjustment can be presented to the user.
Accordingly, sudden color changes occur in the target color and its neighboring colors after an adjustment depending on the contents of the adjustment specified by a user, and problems such as contrast decrease, etc. occur. The conventional techniques, however, cannot predict these problems until an adjustment is made with the above described methods. Means for preparing a plurality of sample images including a plurality of colors, and for verifying the sample images by making a trial color correction conventionally exists. This method, however, requires procedures for setting adjustment values, for displaying a sample image on a screen after making a color adjustment based on the set values, for causing a user to verify whether or not a problem occurs in the output image, and for resetting the adjustment values if a problem occurs. This requires considerable amounts of labor and time.